Double-strand breaks are repaired through one of two mechanisms:
nonhomologous end joining (NHEJ) or homologous recombination repair (HRR)
. In NHEJ, an enzyme called DNA ligase IV uses overhanging pieces of DNA adjacent to the break to join and fill in the ends.
How is DNA damage detected and repaired?
Breaks in DNA reduce the molecular weight of a single DNA strand, and this may be caused by physical, chemical or enzymatic reagents (6).
DNA breaks and lesions may be detected by PCR or using agarose gel electrophoresis
(7). PCR is one of the most frequently used techniques for detecting DNA damage (7).
Why DNA repair is needed by the cell?
DNA repair
ensures the survival of a species by enabling parental DNA to be inherited as faithfully as possible by offspring
. It also preserves the health of an individual. Mutations in the genetic code can lead to cancer and other genetic diseases.
What are the 4 types of DNA repair?
At least five major DNA repair pathways—
base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)
—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.
How does cell repair work?
Like Apollo 13, a damaged cell cannot rely on anyone to fix it. It must repair itself,
first by stopping the loss of cytoplasm, and then regenerate by rebuilding structures that were damaged or lost
. Understanding how they repair and regenerate themselves could guide treatments for conditions involving cellular damage.
What causes DNA damage in cells?
DNA damage occurs continuously as a result of various factors—
intracellular metabolism, replication, and exposure to genotoxic agents, such as ionizing radiation and chemotherapy
. If left unrepaired, this damage could result in changes or mutations within the cell genomic material.
Why is DNA damage repaired before cells enter mitosis?
Ideally, if DNA damage is detected, the cells do not enter mitosis until the damage is repaired. Why is DNA damage repaired before cells enter mitosis?
So that healthy daughter cells are produced, allowing the organism to continue to grow
.
What happens when DNA is damaged?
DNA damage in non-replicating cells, if not repaired and accumulated can lead to aging
. DNA damage in replicating cells, if not repaired can lead to either apoptosis or to cancer.
How is DNA damaged by UV light?
UV radiation causes two classes of DNA lesions:
cyclobutane pyrimidine dimers (CPDs, Figure 1) and 6-4 photoproducts (6-4 PPs, Figure 2)
. Both of these lesions distort DNA's structure, introducing bends or kinks and thereby impeding transcription and replication.
What are the two types of DNA repair?
There are two general classes of DNA repair;
the direct reversal of the chemical process generating the damage and the replacement of damaged nucleotide bases
. DNA encodes the cell genome and is therefore a permanent copy of a structure necessary for the correct functioning of a cell.
Why does a cell repair?
In every cell of the body, DNA suffers damage between 50,000 and 100,000 times a day. This happens when DNA building blocks are swapped or changed around, or where one or both strands of DNA is torn.
When damage occurs, the cell sends repair proteins to the spot to quickly resolve it
.
Does body repair DNA?
Summary:
DNA repair is compromised at important regions of our genome, shedding new light on the human body's capacity to repair DNA damage
, medical scientists have discovered.
How are DNA mutations repaired?
Most of the types of DNA damage that are caused by chemical or physical mutagens (Section 14.1. 1) can only be repaired by
excision of the damaged nucleotide followed by resynthesis of a new stretch of DNA
, as shown in Figure 14.18B.
What enzymes are used in DNA repair?
Apurinic/apyrimidinic (AP) endonuclease 2 (Apex2)
is well-known as an essential DNA repair enzyme that plays a critical role in DNA repair against the oxidative damage in a variety of cells. It has been reported that AP sites occur in DNA molecules by spontaneous hydrolysis, DNA-damaging agents or by DNA glycosylases.
What are the 4 stages of the cell cycle?
In eukaryotes, the cell cycle consists of four discrete phases:
G
1
, S, G
2
, and M
. The S or synthesis phase is when DNA replication occurs, and the M or mitosis phase is when the cell actually divides. The other two phases — G
1
and G
2
, the so-called gap phases — are less dramatic but equally important.
What phase in the cell cycle does DNA replication take place?
S phase
is the period during which DNA replication occurs.
What is the cellular process that enables cells to grow and develop into tissue?
One cell gives rise to two genetically identical daughter cells during the process of mitosis. Encyclopædia Britannica, Inc. Most tissues of the body grow by
increasing their cell number
, but this growth is highly regulated to maintain a balance between different tissues.
How do proteins repair damaged cells?
The muscle damage initiates a repair process in which
certain hormones, along with the macronutrient protein, synthesize new satellite cells
, which are used to repair the damaged muscle fibers. In other words, the role of protein is to help repair tissues damaged by exercise.
Which of the following can damage DNA?
DNA bases can be damaged by: (1) oxidative processes, (2) alkylation of bases, (3) base loss caused by the hydrolysis of bases, (4) bulky adduct formation, (5) DNA crosslinking, and (6) DNA strand breaks, including single and double stranded breaks. An overview of these types of damage are described below.
What are the diseases involving damaged DNA?
Inherited human diseases of DNA repair include many cancer susceptibility syndromes, such as
Xeroderma pigmentosum, Ataxia-telangectasia, Bloom's and Werner's syndromes, Hereditary Non-Polyposis Colon Cancer, Li-Fraumeni-syndrome, and breast/ovarian cancer syndrome
.
